Agitator mill

ABSTRACT

An agitator mill for treating free-flowing grinding stock has a grinding receptacle and an interior stator disposed therein. A rotatably drivable annular cylindrical rotor is disposed between the interior stator and the receptacle wall, with a grinding chamber being defined between said rotor and the receptacle wall. A grinding-stock discharge conduit is formed between the rotor and the interior stator ( 22 ) which is connected to the grinding chamber by means of a deflection conduit. Devices are provided for preventing the carry-over of auxiliary grinding bodies from the grinding chamber into the grinding-stock discharge conduit.

The invention relates to an agitator mill according to the preamble ofclaim 1.

Such an agitator mill is known from EP 0 370 022 B1 (corresponding toU.S. Pat. No. 5,062,577). In this agitator mill, the auxiliary grindingbodies are centrifuged from the flow of grinding stock and auxiliarygrinding bodies via the auxiliary-grinding-body return conduits beforesaid flow reaches the protective screen. The basic function of theprotective screen is to collect worn-out auxiliary grinding bodies whichare too light to be thrown out via the auxiliary-grinding-body returnconduits, thus serving as a throttle device for generating acounter-pressure counteracting the flow of grinding stock. The agitatoris provided with agitator implements protruding into the exteriorgrinding chamber. When using extremely small auxiliary grinding bodies,it is not ensured that the auxiliary grinding bodies will not eventuallyreach the protective screen, thus gradually clogging the latter. Inparticular when using extremely small auxiliary grinding bodies, it isrequired to use correspondingly fine protective screens which in turnmay be damaged very easily, should they be hit by auxiliary grindingbodies. If, however, relatively viscous grinding stocks are to betreated by using auxiliary grinding bodies of a usual size, a partiallyclogged protective screen leads to a substantial pressure build-up inthe agitator mill, which also results in a disturbance of the grindingprocess.

An agitator mill is known from EP 0 504 836 B1 which has a cup-shaperotor disposed in a cylindrical housing, said rotor being provided withpassage slots along the length thereof. An interior stator comprising aprotective screen is disposed within the rotor. The exterior grindingchamber is provided with implements that are fixed to both the rotor andthe wall de-limiting the grinding chamber. This agitator mill is notsuitable for the use of extremely small auxiliary grinding bodies.Moreover, said mill is subject to the same problems as already describedabove.

An agitator mill is known from DE 34 37 866 A1 (corresponding to U.S.Pat. No. 5,011,089), said agitator mill having a rotor withpaddle-shaped implements disposed on the outside thereof. A protectivescreen is disposed within the rotor. The rotor is composed of axiallyparallel bars to which the paddle-shaped implements are fastened. Thegrinding stock is supplied radially. Owing to the paddle-shaped designof the agitator implements, this agitator mill ensures a concentrationof auxiliary grinding bodies to be obtained in the area of thereceptacle wall; a defined grinding, in particular by means of extremelysmall auxiliary grinding bodies as well as a reliable separation of theauxiliary grinding bodies without the risk of operational failures ishowever not obtainable either. Since the grinding stock flows throughthe packing of auxiliary grinding bodies in a radial direction, thegrinding stock is subject to a grinding process over a very shortdistance only. Accordingly, if the grinding stock passes through theagitator mill only once, only a moderate grinding progress is obtained.

An agitator mill of the generic type is known from DE 196 38 354 A1(corresponding to U.S. Pat. No. 5,894,998), said agitator mill having aprotective screen fixed to the cup-shaped rotor which is sealed againstthe interior stator by means of a mechanical seal. The protective screenthus co-rotates with the rotor, thereby ensuring that auxiliary grindingbodies reaching said filter are thrown out even more efficiently.

It is the object of the invention to develop an agitator mill of thegeneric type in a way as to obtain a grinding and disperging effect witha narrow particle distribution even if the grinding stock passes throughthe agitator mill only once, in particular when using auxiliary grindingbodies having an extremely small diameter, whilst avoiding the risk ofoperational failures, caused in particular by auxiliary grinding bodieshitting the protective screen.

This object is attained according to the invention by the features inthe characterizing part of claim 1. The crux of the invention is thatauxiliary grinding bodies are only located in the grinding chamberbetween the rotor and the receptacle wall and are concentrated in saidgrinding chamber. Concentrating the auxiliary grinding bodies in saidgrinding chamber already ensures that said auxiliary grinding bodies donot enter the grinding-stock discharge conduit. Fastened to the rotor,the implements extend as far as into the vicinity of the receptaclewall, thereby ensuring that the auxiliary grinding bodies areaccelerated outward and concentrated together. The grinding stock flowsthrough the close-packed grinding stock in the axial direction so as toobtain a uniform grinding and dispersion. Along with the measures forconcentrating auxiliary grinding bodies in the annular exterior grindingchamber, devices are provided for effectively preventing the auxiliarygrinding bodies from reaching the protective screen. The grinding-stockdischarge conduit, which is located within the rotor and is defined bythe rotor and the interior stator, contains no or only very fewauxiliary grinding bodies, thereby effectively eliminating the drawbacksdescribed above.

The measures according to claims 2 to 4 contribute to a concentration ofthe auxiliary grinding bodies in the grinding chamber.

The measures according to claims 5 to 7 further help to prevent theauxiliary grinding bodies from entering the deflection conduit.

The development according to claim 8 prevents the few auxiliary grindingbodies that do reach the grinding-stock discharge conduit fromdepositing, thereby causing them to remain in the flow towards theauxiliary-grinding-body return conduits where they are re-supplied intothe beginning of the grinding chamber. The measures according to claim 9ensure that the auxiliary grinding bodies are furthermore accelerated inthe direction of the auxiliary-grinding-body return conduits.

The development according to claim 10 prevents a layer of grinding stockand auxiliary grinding bodies from forming at the inside of the rotorthat no longer takes part in the process.

The development according to claim 11 is particularly advantageous inconjunction with the measures according to claims 8 to 10 owing to theparticularly intensive cooling of in particular temperature-sensitivegrinding stock in the grinding-stock discharge conduit without requiringany additional supply of energy, said grinding stock thus being subjectto high energy only during the actual grinding process in the grindingchamber.

The embodiment according to claim 12 enables auxiliary grinding bodiespresent in the grinding-stock discharge conduit to be directly thrownoutward into the grinding chamber, this effect being promoted by thedevelopment according to claim 13.

Appropriate diameter ranges for extremely small auxiliary grindingbodies are stated in claim 14.

Further features, advantages and details will become apparent from theensuing description of embodiments of the invention, taken inconjunction with the drawing, in which

FIG. 1 shows a schematic lateral view of an agitator mill;

FIG. 2 shows a vertical longitudinal section through a first embodimentof an agitator mill;

FIG. 3 shows a true length of the outside of the rotor of the agitatormill according to FIG. 2;

FIG. 4 shows a lateral view of the interior stator of the agitator millaccording to FIGS. 2 and 3;

FIG. 5 shows a vertical longitudinal section through a second embodimentof the agitator mill;

FIG. 6 shows a true length of the inside of the rotor of the agitatormill according to FIG. 5,

FIG. 7 shows a vertical longitudinal section through a third embodimentof the agitator mill;

FIG. 8 shows a vertical longitudinal section through a fourth embodimentof the agitator mill; and

FIG. 9 shows a longitudinal section through a fifth embodiment of theagitator mill.

The agitator mill shown in FIG. 1 has a stand 1 in the usual manner towhich a cylindrical grinding receptacle 2 may be fixed. This stand 1houses an electric drive motor 3 which is provided with a V-belt pulley4 for rotatably driving a V-belt pulley 7, which is connected to a driveshaft 6 in a non-rotational manner, by means of V-belts 5.

As can be seen in particular from FIGS. 2 and 3, the grinding receptacle2 has a cylindrical receptacle wall 9 surrounding a grinding chamber 8,said receptacle wall 9 being surrounded by a substantially cylindricalcooling casing 10. The receptacle wall 9 and the cooling casing 10define a cooling chamber 11 between each other. The lower closingelement of the grinding chamber 8 is formed by a circular bottom plate12 which is fastened to the grinding receptacle 2 by means of screws 13.

The grinding receptacle 2 has an upper annular flange 14 by means ofwhich it is fastened to the underside of a support housing 15 by meansof screws 16, said support housing 15 being fixed to the stand 1 of theagitator mill. The grinding chamber 8 is closed by a lid 17. The supporthousing 15 has a central bearing and sealing housing 18 which is alignedcoaxially with the central longitudinal axis 19 of the grindingreceptacle 2. This bearing and sealing housing 18 is penetrated by thedrive shaft 6 which also extends coaxially with the axis 19 and isprovided with an agitator 20.

A grinding-stock supply line 21 projects into the area of the bearingand sealing housing 18 neighbouring the grinding chamber 8.

An approximately cup-shaped, cylindrical interior stator 22 projectinginto the grinding chamber 2 is disposed on the bottom plate 12, saidinterior stator 22 having an outer wall 23 aligned coaxially with theaxis 19 and a cylindrical inner casing 24 within said outer wall 23.Between each other, the outer wall 23 and the inner casing 24 define acooling chamber 25 of the interior stator 22. The cooling chamber 25 issupplied with cooling water via a cooling-water supply connector 26,said cooling water being discharged via a cooling-water dischargeconnector 27. The cooling chamber 11 of the grinding receptacle 2 issupplied with cooling water via a cooling-water supply connector 28,said cooling water being discharged via a cooling-water dischargeconnector 29.

As shown in the drawing, a protective screen 30 is disposed at the upperend of the interior stator 22, said protective screen 30 being connectedto a grinding-stock discharge line 31. In the area of the bottom plate12, the discharge line 31 is provided with a handle 32 which isdetachably connected to the bottom plate 12 by means of screws 33.

The protective screen 30 is sealed against the interior stator 22 bymeans of a seal 34 and may be, together with the discharge line 31,pulled downwards out of the interior stator 22 after loosening thescrews 33.

The agitator 20 has a cup-shaped basic structure, thus having asubstantially annular cylindrical rotor 35. The agitator 20 has alid-type closing member 36 of the rotor 35 at the upper end thereof. Anauxiliary-grinding-body return device 37 is disposed in the agitator 20,strictly speaking in the transition area between the lid-type closingmember 36 and the annular cylindrical, i.e. tubular, rotor 35.

The following applies to the radial width a of the grinding chamber 8:a=(D9−D35)/2, with D9 being the diameter of the receptacle wall 9, i.e.the external diameter of the grinding chamber 8, and with D35 referringto the external diameter of the rotor 35, i.e. the internal diameter ofthe ding chamber. The following applies:

0.6≦D35/D9≦0.95, and preferably, 0.7≦D35/D9≦0.85.

The inside of the receptacle wall 9 is cylindrically smooth, having noimplements projecting into the annular grinding chamber 8. On the otherhand, the outside of the equally cylindrical rotor 35 is provided withpeg-style implements 38 radially projecting into the grinding chamber 8with respect to the central longitudinal axis 19. Said implements 38almost extend as far as the receptacle wall 9, thus only leaving a gap39 determined by construction and having a gap width b. As can be seenfrom FIG. 3, the implements 38 are helically disposed along the rotorsurface. The implements 38 are disposed in the first area 40 assigned tothe closing member 36 and are disposed along a first helical curve 41which is formed in a way as to enable the implements 38 to have atransport effect on the auxiliary grinding bodies 43, which are presentin the grinding chamber 8 and have a diameter c, downwards in thedirection of flow 44 of the grinding stock, i.e. towards the bottomplate 12, when the agitator mill 20, and therefore the rotor 35, rotatesin the direction of rotation 42. This first area 40 comprising theimplements 38 disposed along the first helical curve 41 approximatelyextends as far as the lower side of the return device 37, as can be seenfrom FIG. 3.

In a second area 45 below the first area 40, the implements 38 aredisposed along a second helical curve 46 extending in the oppositedirection, with the momentum thus imparted to the auxiliary grindingbodies 43 being directed opposite to the direction of flow 44 of thegrinding stock when the agitator 20 is driven in the direction ofrotation 42. As can be seen from FIG. 3, implements 38 disposed next toone another in the circumferential direction of the rotor 35 aredisposed both along the first helical curve 41 and along the secondhelical curve 46 in a way as to overlap with one another in thedirection of the central longitudinal axis 19, thus ensuring that thereceptacle wall 9 is completely wiped by the implements 38 for everyrevolution of the rotor 35.

An annular cylindrical grinding-stock discharge conduit 47 is formedbetween the rotor 35 and the outer wall 23 of the interior stator 22.The outer wall 23 of the interior stator 22 is provided with peg-stylewiper elements 48 radially projecting outwards into the dischargeconduit 47. As can be seen from FIG. 4, wiper elements 48 disposed nextto one another in the circumferential direction of the interior stator22 are disposed in the direction of the central longitudinal axis 19 ina way as to overlap with one another, thus ensuring that for everyrevolution of the rotor 35, the wall thereof is completely wiped by saidelements 48. Said elements 48 are disposed along a helical curve whichextends in a way that when the rotor 35 is driven in the direction ofrotation 42, this enables them to impart a momentum, in the direction offlow 44, to auxiliary grinding bodies 43 that may have entered thedischarge conduit 47. The wiper elements 48 have a gap 49 in relation tothe interior stator 22, the gap width e thereof not exceeding theminimum width required by construction.

The following applies to the gap width b of the gap 39 in relation tothe diameter c of the auxiliary grinding bodies 43: 4c≦b≦6c, with aminimum marginal condition of 1.0 mm≦b≦2.0 mm being defined for the useof particularly small auxiliary grinding bodies 43. Correspondingly, thefollowing applies to the gap width e of the gap 49 in relation to thediameter c of the auxiliary grinding bodies 43: 4c≦e≦6c, with theminimum marginal condition of 1.0 mm≦e≦2.0 mm equally applying to theuse of extremely small auxiliary grinding bodies. This design enablesthe implements 38 to constantly swirl the packing of auxiliary grindingbodies in the grinding chamber 8. When driven, the rotor 35 is uniformlywiped by the wiper elements 48 owing to the small gap width e. Whenusing auxiliary grinding bodies 43 of an extremely small diameter c,i.e. micro-auxiliary grinding bodies, the following applies to thediameter c thereof: 20 μm≦c≦100 μm.

The discharge conduit 47 has a radial width f to which applies:f=(d35−d23)/2, with d35 referring to the internal diameter of the rotor35, i.e. the external diameter of the discharge conduit 47, and d23referring to the external diameter of the interior stator 22, i.e. theinternal diameter of the discharge conduit 47. The following applies:0.8≦d23/d35≦0.98, and preferably 0.9≦d23/d35≦0.98. The grinding chamber8 is connected to the discharge conduit 47 by means of a deflectionconduit 50, the width thereof approximately equalling that of thedischarge conduit 47, as can be seen from FIG. 2. Said deflectionconduit 50 thus surrounds the free lower end of the rotor 35. Adjacentto the deflection conduit 50, the grinding chamber 8 is substantiallyclosed by means of a bottom surface 51 extending radially toward theaxis 19, with the lowest, i.e. next adjacent implement 38 rotating inclose proximity to said bottom surface 51 at a distance g approximatelyequalling that of the gap widths b and e. Therefore, it is also in thisarea that auxiliary grinding bodies 43 are accelerated radially outwardjust before entering the deflection conduit 50 so as to be transportedaway from the deflection conduit 50.

As indicated in FIG. 2, the cylindrical protective screen 30 is composedof a stack of annular disks 52 which are spaced apart from one anotherso as to form a separation gap 53 between two disks 52 each, the widththereof being smaller than the diameter c of the smallest auxiliarygrinding bodies 43 in use. The front side, i.e. the side facing towardsthe shaft 6, of the stack of annular disks 52 is closed by means of aclosing plate 54. The protective screen 30 is disposed within the returndevice 37.

As can be seen from FIGS. 2 and 3, auxiliary-grinding-body returnconduits 55 are formed in the return device 37. The respective inlet 56thereof is directly adjacent to the return conduit 47 and to theprotective screen 30. The respective outlet 57 thereof projects into thebeginning area of the grinding chamber 8, strictly speaking into thefirst area 40 of the helically disposed implements 38. As can be seenfrom FIG. 3, the respective outlets 57 are disposed directly in front ofone or several implements 38 when seen in the direction of rotation 42,thereby imparting a momentum to auxiliary grinding bodies 43 returningvia a discharge conduit 47 in the direction of flow 44 as soon as theyhave been discharged through the outlet 57.

When flowing through the grinding chamber 8 in the direction of flow 44,the grinding stock flows downward from the grinding-stock supply line 21through a grinding-stock supply chamber 58 disposed between the closingmember 36 of the agitator 20 and the lid 17, the first area 40 and thesecond area 45 of the grinding chamber 8 before flowing radially inwardvia the deflection conduit 50 and from there, upward into a dischargeconduit 59 via the grinding-stock discharge conduit 47, said dischargeconduit 59 being formed between the closing member 36 and the interiorstator 22 and substantially extending radially inward towards theprotective screen 30. Afterwards, the grinding stock passes through theprotective screen 30 to enter the grinding-stock discharge line 31through which it is discharged from the agitator mill.

When passing through the grinding chamber 8, the grinding stock isground due to the rotating agitator 20 in cooperation with the auxiliarygrinding bodies 43. An amount of tangential momentum is imparted to theauxiliary driving bodies by the implements 38, thereby moving them inthe direction of the receptacle wall 9. As indicated in the drawing,this causes the auxiliary grinding bodies 43 to be concentrated in theradially outer area of the grinding chamber 8. The small width b of thegap 39 between the implements 38 and the receptacle wall 9 preventsauxiliary grinding bodies 43 from depositing at the receptacle wall 9;even auxiliary grinding bodies 43 that have moved there are activatedand entrained over and over again. The already described arrangement ofimplements 38 along the two helical curves 41 and 46 prevents theauxiliary grinding bodies 43 in the upper first area 40 from flowingback into the grinding-stock supply line 21 via the grinding-stocksupply chamber 58. The arrangement of the agitator implements in thesecond area 45 prevents auxiliary grinding bodies 43, or at least mostof them, from entering the discharge conduit 47 via the deflectionconduit 50. This gives rise to a turbulent flow in the grinding chamber8 characterized by strongly interacting vortices within the grindingstock when flowing through the grinding chamber 8, thereby preventing alinear movement thereof. This causes the individual grinding-stockparticles to alternately flow from the rotor 35 to the receptacle wall 9and vice versa. In the direction of flow 44, the throughput of theagitator mill is superimposed on this radially reciprocating flow, withthe magnitude of the velocity component in the direction of flow 44being obtained from the volumetric throughput of grinding stock per unitof time and the free cross-section of the grinding chamber 8, strictlyspeaking the cross-section of the grinding chamber 8 minus thecross-section of the available auxiliary grinding bodies 43.

If auxiliary grinding bodies 43 do manage to enter the grinding-stockdischarge conduit 47 despite the described measures, they aretransported through the entire discharge conduit 47 together with thegrinding stock by means of the wiper elements 48 before being returnedinto the first area 40 of the grinding chamber 8 via the return device37.

The embodiment according to FIG. 5 differs from that according to FIG. 2only in that additional, small auxiliary-grinding-body return conduits60 in the shape of bores are formed along the axial length of the rotor35′ which are distributed along the circumference thereof and have adiameter h of 5.0 to 30.0 mm. From the annular cylindricalgrinding-stock discharge conduit 47, said return conduits 60 thusdirectly project into the second area 45 of the grinding chamber 8,thereby ensuring that auxiliary grinding bodies 43 that have entered thegrinding-stock discharge conduit 47 despite the described measures arealready returned into the grinding chamber 8 before reaching the upperreturn device 37.

As can be seen from the true length of the inside of the rotor 35′ shownin FIG. 6, the small auxiliary-grinding-body return conduits 60 aredisposed along helical curves, said conduits 60 being disposed next toone another so as to overlap with one another in the circumferentialdirection, thereby ensuring that auxiliary grinding bodies 43 that havemanaged to enter the grinding-stock discharge conduit 47 and have beencentrifuged off the rotor 35 are forced to flow by at least one suchconduit 60 through which they may be returned into the exterior grindingchamber 9.

The embodiment according to FIG. 7 differs from that according to FIG. 2only in that the protective screen 30′ has a support body 61 connectedto the interior stator 22 in a known manner, said support body 61 beingprovided with slot-like openings 62. A very thin piece of sheet metal ora film 63, respectively, is disposed on the outside of said support body61, said film 63 being provided with very fine separating slots 64 thetrue width of which cannot be represented in the drawing but is clearlysmaller than the diameter c of the smallest auxiliary grinding bodies43.

The agitator mill according to FIG. 8 differs from that according toFIG. 2 in that the rotor 35′ is provided with theauxiliary-grinding-body return conduits 60 according to the embodimentof FIG. 5 and the protective screen 30′ according to the embodiment ofFIG. 7.

The embodiment according to FIG. 9 basically corresponds to thataccording to FIGS. 5 and 7, with the rotor 35′ being provided with theauxiliary-grinding-body return conduits 60. The protective screen 30″,however, is not fixed to the interior stator 22 but is disposed in theclosing member 36 of the rotor 35′ in which a cylindrical recess 65 isformed that encloses or comprises, respectively, all of the protectivescreens 30, 30′, 30″. The protective screen 30″ has a support body 66which is secured to the closing member 36 of the rotor 35′ by means of ascrew 67. The support body 66 is provided with slot-like openings 62,with its cylindrical outer circumference being covered by a foil or apiece of sheet metal 63, respectively, comprising separating slots 64. Adischarge 68 is formed in the support body 66, said discharge 68 havinga discharge opening 69, which is concentric with the axis 19, on theside facing towards the interior stator 22′. The grinding-stockdischarge line 31′ extends through the otherwise closed upper front wall70 of the interior stator 22′ in a sealed manner as far as into thevicinity of the facing closing wall 71 of the protective sleeve filter30″. A narrow gap 72 is formed between the grinding-stock discharge line31′ and said closing wall 71. Said gap 72 usually has a width i which issmaller than the smallest diameter c of the auxiliary grinding bodies43. The width i of the gap 72 must be small enough for a sufficientlyhigh pressure loss to occur when the ground grinding stock isdischarged, thereby allowing the grinding stock to be discharged throughthe protective screen 30″.

The closing wall 71 of said protective screen 30″ opens towards thefront wall 70 in the shape of a truncated cone, thereby defining anannular gap 73 at the radially outer area thereof facing towards thefront wall 70, said annular gap 73 allowing virtually no auxiliarygrinding bodies 43 to enter when the agitator mill is in use. Auxiliarygrinding bodies 43 that may have entered this area during standstill arethrown outward again through the annular gap 73 so as to enter theauxiliary-grinding-body return conduits 55.

In this embodiment, the protective screen 30″, together with the foil orpiece of sheet metal 63 thereof, respectively, is also perfectly alignedwith the auxiliary-grinding-body return conduits 55 in the axialdirection. In case any auxiliary grinding bodies 43 do manage to enterthe area of the protective screen 30″, they are also thrown into thereturn conduits 55 by the foil or piece of sheet metal 63, respectively,forming the cylindrical circumference thereof.

Although each of the previously described embodiments shows agitatormills having a vertical central longitudinal axis 19, the describedembodiments may easily be fitted in a horizontal position or in anintermediate position.

In case of using auxiliary grinding bodies 43 of an extremely smalldiameter c, i.e. micro-auxiliary grinding bodies, the grinding stock hasa very low viscosity in the range of 1 to 100 mPas.

1-17. (canceled)
 18. An agitator mill for treating free-flowing grinding stock, comprising a grinding receptacle (2) which defines a substantially closed grinding chamber (8) by means of a receptacle wall (9) and an agitator (20) which is rotatably drivably disposed in the grinding receptacle (2) in a direction of rotation (42) and which is cup-shaped with respect to a common central longitudinal axis (19), and which has an annular cylindrical rotor (35, 35′) which is provided with implements (38) extending as far as into the vicinity of the receptacle wall (9), and an interior stator (22, 22′) which is disposed within the rotor (35, 35′), which is joined to the grinding receptacle (2), and which has a closed outer wall (23), wherein the annular cylindrical grinding chamber (8) is formed between the receptacle wall (9) and the rotor (35, 35′) and receives auxiliary grinding bodies with a diameter c, and wherein an annular cylindrical interior chamber in the shape of an annular gap is formed between the rotor (35, 35′) and the outer wall (23) of the interior stator (22, 22′), said interior chamber being disposed coaxially within the grinding chamber (8) and connected thereto via a deflection conduit (50), and wherein the grinding chamber (8) is at least partially filled with auxiliary grinding bodies (43), and wherein a grinding-stock supply chamber (58), which is disposed upstream of the grinding chamber (8) and opens into the latter in a direction of flow (44), and a protective screen (30, 30″), which is disposed downstream of the interior chamber (8) in the direction of flow (44), are disposed approximately on the same side of the grinding receptacle (2) for the grinding stock to pass through, and wherein auxiliary-grinding-body return conduits (55) are provided in the agitator (20) for returning the auxiliary grinding bodies (43) from the vicinity of the protective screen (30, 30″) into the grinding chamber (8), said return conduits (55) connecting the end of the interior chamber to the beginning of the grinding chamber (8), and wherein the receptacle wall (9) is free of implements, wherein the implements fixed to the rotor (35, 35′) leave only a narrow gap (39) in relation to the receptacle wall (9), wherein the interior chamber is a grinding-stock discharge conduit (47), and wherein the implements (38) fixed to the rotor (35, 35′) serve as devices for preventing a carry-over of auxiliary grinding bodies (43) from the grinding chamber (8) into the grinding-stock discharge conduit (47) and are disposed along a helical curve (46) in an area (45) between the auxiliary-grinding-body return conduits (55) and the deflection conduit (50) in the circumferential direction of the rotor (35, 35′) so as to overlap with one another, thereby imparting a momentum to the auxiliary grinding bodies (43) that is opposite to the direction of flow (44) when the rotor (35, 35′) is rotatably driven in a direction of rotation (42).
 19. An agitator mill according to claim 18, wherein the gap (39) between the implements (38) and the receptacle wall (9) has a gap width b to which applies in relation to the diameter c of the auxiliary grinding bodies (43): 4c≦b≦6c, the minimum gap width b being defined as: 1.0 mm≦b≦2.0 mm.
 20. An agitator mill according to claim 18, wherein the grinding chamber (8) has a bottom surface (51) upstream of the deflection conduit (50), said bottom surface (51) being wiped by the nearest implement (38) while leaving a distance g uncovered.
 21. An agitator mill according to claim 20, wherein the following applies to the distance g between the bottom surface (51) and the nearest implement (38) in relation to the diameter c of the auxiliary grinding bodies (43): 4c≦g≦6c, with the minimum distance g being defined as: 1.0 mm≦g≦2.0 mm.
 22. An agitator mill according to claim 20, wherein the deflection conduit (50) projects out of the grinding chamber (8) directly next to the rotor (35, 35′) and wherein the bottom surface (51) is disposed radially beyond thereof.
 23. An agitator mill according to claim 18, wherein wiper elements (48) extending towards the rotor (35, 35′) are disposed along the interior stator (22, 22′), and in that the rotor (35, 35′) is free of implements on the inside thereof defining the grinding-stock discharge conduit (47).
 24. An agitator mill according to claim 23, wherein the wiper elements (48) disposed along the interior stator (22, 22′) overlap with one another in the direction of the central longitudinal axis (19) and are disposed along a helical curve in the circumferential direction of the interior stator (22, 22) in a way as to impart a momentum to the auxiliary grinding bodies (43) in the direction of flow (44) when the rotor (35, 35′) is driven in the direction of rotation (42).
 25. An agitator mill according to claim 23, wherein the wiper elements (48) leave a gap (49) in relation to the rotor (35, 35′) to the gap width e thereof applies the following in relation to the diameter c of the auxiliary grinding bodies (43): 4c≦e≦6c, with a minimum gap width e being defined as: 1.0 mm≦c≦2.0 mm.
 26. An agitator mill according to claim 18, wherein the interior stator (22, 22′) is provided with a cooling chamber (25).
 27. An agitator mill according to claim 18, wherein small auxiliary-grinding-body return conduits (60) connecting the grinding-stock discharge conduit (47) to the grinding chamber (8) are formed in the rotor (35′) to the diameter h thereof applies: 5.0 mm≦h≦30.0 mm.
 28. An agitator mill according to claim 27, wherein the auxiliary-grinding-body return conduits (60) are disposed to overlap with one another in the direction of the central longitudinal axis (19) and along a helical curve rising from the deflection conduit (15) towards the protective screen (30, 30′, 30″) in the direction of rotation (42).
 29. An agitator mill according to claim 18, wherein the following applies to the diameter c of the auxiliary grinding bodies (43): c≦0.3 mm.
 30. An agitator mill according to claim 18, wherein the following applies to the diameter c of the auxiliary grinding bodies (43): 0.02 mm≦c≦0.1 mm.
 31. An agitator mill according to claim 18, wherein the protective screen (30″) is joined to the agitator (20) in a non-rotational manner, and wherein a discharge (68) of the protective screen (30″) directly projects into a grinding-stock discharge conduit (31′) which is stationary with respect to the grinding receptacle (2).
 32. An agitator mill according to claim 18, wherein the following applies to the relationship between the internal diameter D35 of the grinding chamber (8) and the external diameter D9 of the grinding chamber (8): 0.6≦D35/D9≦0.95.
 33. An agitator mill according to claim 18, wherein the following applies to the relationship between the internal diameter D35 of the grinding chamber (8) and the external diameter D9 of the grinding chamber (8): 0.7≦D35/D9≦0.85.
 34. An agitator mill according to claim 18, wherein the following applies to the relationship between the internal diameter d23 of the discharge conduit (47) and the external diameter d35 of the discharge conduit (47): 0.8≦d23/d35≦0.98.
 35. An agitator mill according to claim 18, wherein the following applies to the relationship between the internal diameter d23 of the discharge conduit (47) and the external diameter d35 of the discharge conduit (47): 0.9≦d23/d35≦0.98. 